Process for the production of diols

Abstract

The invention relates to a process for the production of diols with a special structure which are characterized by formula (I). These diols are substances which, besides two OH groups, contain a C═C double bond so that they are suitable as monomers for the production of polymers. The process comprises hydrolyzing a corresponding cyclic precursor in aqueous medium in the presence of an acid dissolved in that medium, the hydrolysis being accompanied by the elimination of a carbonyl compound, and subsequently neutralizing the acid present in the reaction mixture with a base, the base having a pKb value above 0.18 and preferably above 3.0 and being present in heterogeneous form.

1. A process for the production of polymerizable monomers corresponding to formula (I): 
       
         
           
           
               
               
           
         
         in which the substituent R 1  is hydrogen or a C 1-4  alkyl group, 
         R 2  to R 4  independently represent hydrogen or an aliphatic, cycloaliphatic or aromatic moiety, 
         X is a group —(CH 2 ) n  and n is the number 0 or 1, 
         Y is a group —(CHR 5 ) m , and m is the number 0, 1 or 2, and R 5  is hydrogen or an OH group, the process comprising the steps of:
 (a). hydrolyzing a compound corresponding to formula (II): 
 
       
       
         
           
           
               
               
           
         
         
           in which the substituents R 1 , R 2  to R 4 , X and Y are as defined above and the substituents 
         
         R 6  and R 7  independently represent hydrogen or an aliphatic group,
 in aqueous medium and in the presence of an acid dissolved in the aqueous medium to form a mixture, the hydrolysis being accompanied by elimination of a compound (III): 
 
       
       
         
           
           
               
               
           
         
         
           in which R 6  and R 7  are as defined above, and 
           (b) contacting said mixture with a weak base to neutralize the acid present in the mixture, said base having a pK b  value above 0.18 and being present in heterogeneous form. 
         
       
     
     
       2. The process as claimed in  claim 1  wherein said base has a pK b  value above 3.0 and is present in heterogeneous form. 
     
     
       3. The process as claimed in  claim 2  wherein said base is in an immobilized form. 
     
     
       4. The process as claimed in  claim 3  wherein said base comprises a basic ion exchange resin. 
     
     
       5. The process of  claim 1  wherein R 1  is hydrogen or a methyl group, R 2 , R 3  and R 4  represent hydrogen, X is a group -(CH 2 ) n  and n is the number 0, and Y is a group -(CH 2 ) m  and m is the number 1. 
     
     
       6. The process as claimed in  claim 5  wherein R 1  is a methyl group and R 6  and R 7  are methyl groups. 
     
     
       7. The process of  claim 1  wherein said acid comprises a mineral acid. 
     
     
       8. The process as claimed in  claim 7 , wherein said mineral acid is selected from the group consisting of sulfuric acid, hydrochloric acid and hydrobromic acid. 
     
     
       9. The process of  claim 4  wherein said basic ion exchange resin contains amine functions. 
     
     
       10. The process as claimed in  claim 9  wherein said amine functions comprise tertiary amines. 
     
     
       11. The process as claimed in  claim 10  wherein said basic ion exchange resin is selected from the group consisting of Amberlite IRA96RF, Amberlyst A21, Amberlyst A23, Amberlyst A24, Dowex 66, Dowex Monosphere 66, Dowex Monosphere 77, Dowex Marathon WBA, Dowex Marathon WBA-2, Dowex UPCORE Mono WB-500, XUS 43594.00 and Dowex M-43. 
     
     
       12. The process of  claim 1  wherein a gas stream is passed through the mixture during the hydrolysis step to remove the compound (III) released from the reaction mixture. 
     
     
       13. The process as claimed in  claim 12  wherein said gas is air. 
     
     
       14. The process as claimed in  claim 12  wherein the hydrolysis step is carried out by continuous introduction of water at a constant volume. 
     
     
       15. The process of  claim 1  wherein compound (II) is hydrolyzed in the presence of an inhibitor. 
     
     
       16. The process as claimed in  claim 15  wherein said inhibitor comprises hydroquinone monomethyl ether (MEHQ). 
     
     
       17. The process of  claim 1  wherein the hydrolysis is carried out in the absence of organic solvents. 
     
     
       18. The process of  claim 1  wherein the neutralization step is followed by filtration. 
     
     
       19. The process as claimed in  claim 18  wherein the aqueous solution of (I) obtained after filtration is freed from water by stripping. 
     
     
       20. The process as claimed in  claim 19  wherein a thin film evaporator is used for said stripping. 
     
     
       21. The process of  claim 1  wherein the neutralization step is carried out discontinuously. 
     
     
       22. The process of  claim 1  wherein the neutralization step is carried out continuously.